1. Field of the Invention
The present invention relates to a correlation processor for a receiver such as a radar, and particularly, to a technique of suppressing side lobes and lowering S/N loss.
2. Description of the Related Art
For example, Japanese Unexamined Patent Application Publication No. 4-357485 discloses a radar signal processor used for a radar and employing a pulse compression method. This radar signal processor transmits a chirp signal (linear FM signal) toward a target that is relatively moving, receives a reflected signal from the moving target, extracts a Doppler shift component which is caused by the moving target, from the received signal, and detects the moving target according to the extracted Doppler shift component.
After receiving an in-pulse modulated signal that is a chirp signal formed by modulating a long pulse, the pulse compression method obtains a short-pulse signal through a pulse compression filter appropriate for the in-pulse modulated signal. The pulse compression method is used in many radars because it is advantageous in extending a detection range by increasing in-pulse transmission energy, increasing a range resolution, and suppressing interfering and jamming signals.
Generally, the performance of a conventional radar (chirp radar) is evaluated with a waveform (output waveform) after the pulse compression process, more precisely, the pulse width of a main lobe (main lobe width), the levels of side lobes (side lobe levels), and the S/N loss of a peak value of the main lobe.